This program divides naturally into three projects: Metabolism of chemical carcinogens; mutagenic activity of drugs and drug metabolites; protein variation as demonstrated by zone electrophoresis. Most chemical carcinogens undergo metabolism to the active form within the body cells, and undergo further metabolism to the inactive or detoxified forms. This ongoing study emphasizes measurement of activity of certain enzymes involved in metabolism of the carcinogens, particularly in human tissues. Enzymes measured included those metabolizing the polycyclic hydrocarbons, using short-term cultured lymphocytes as a tissue source. Individuals vary considerably in the activities of these enzymes and these studies continue to support evidence that activities of the enzymes correlate with the occurrence of lung cancer and carcinoma of the nasopharynx. Other studies on active forms of carcinogens involve use of bacterial mutagen assays. The bacterial mutagen assays are also being used to study mutagenic effects of certain drugs and drug metabolites. The two groups of drugs thus far studied are the hydralazines, antihypertensive drugs, and the phenyltriazines, which are antitumor agents. Mutagenic activity has been found in certain forms of each of these groups of drugs. Ongoing studies utilizing zone electrophoresis for demonstrating genetic differences in proteins have been used the past year in extending taxonomic studies of certain strains of bacteria, and by a recent methodologic modification, to study newly synthesized proteins in developing embryos by an autoradiographic technique.